now he's 37, the youngest mayor of a top 50 city in the united states. he's also used to the baby face jokes. one of the funnier things that has happened to you when you first met president obama, he jokingly asked if you were the intern. >> that's right. yeah. >> you being asked to do this speech, is that kind of making up for that jab? >> i don't know. i don't know. but i accept, you know, i always got the age jokes at different points in my career. >> is it still happening? >> every now and then. you know, i'm starting to get the gray hair that i need from my 3-year-old daughter and from politics. >> reporter: this is the biggest speech of castro's career. latinos enjoyed prominent speaking roles at the republic an convention, and castro must convince latinos to stick with president obama and turn out in big numbers. there are a lot of latino leaders out there who say president obama has not been a friend of the latino community. >> under any score, immigration, education, health care, on any number of issues he has been a very effective advocate for